Perfluoropolyethers have long been recognized for their outstanding thermal properties and their wide liquid ranges. These properties make the polymers outstanding bases for high performance lubricants. Most perfluoropolyether lubricants are comprised of perfluoropolyether oils containing polytetrafluoroethylene (TFE; Teflon.RTM. polymer) fillers which serve to thicken the oil into a paste. However, some problems are associated with perfluoropolyether-based lubricants containing Teflon.RTM. polymer as filler.
Although these greases have adequate shelf lives often exceeding several years, they have a tendency to separate into two phases, an oil phase and a solid phase, when subjected to high temperatures. For example at 400.degree. F., approximately 11% of the oil in a Teflon.RTM.-based Krytox.RTM. grease separates in 30 hours into a clear phase leaving behind a much thicker paste. The degree of separation is much more pronounced as the temperature is raised still higher.